I've been having problems with my fan not turning on when it's supposed to. I did rig up a toggle switch in the dash and it works just fine, so the fan itself works, and also I beleive that means my relay is good as well since I'm grounding it right off the ecm. So that leads me to the fan switch. I've read about the GN switch that turns on at a lower temp. How does this work, I thought the ECM determined when to turn it on? Do they work with each other, which ever one says go first it goes? And for this GN fan switch, is there any perticular one I should ask for?

btw, it's an 86 tpi 5.0 with a single fan.

Secondly, in the picture Vader uses to show the CTS location, the one on the right missing the wires is the cts if I'm not mistaken, what's the sensor to the left of it?

 

Just look to see if you have the switch. It's on the passenger-side head between #6 and #8. The ECM does control your fan. A temp switch is typically used on cars with dual fans, to control the secondary cooling fan, or TBI cars, since the ECM doesn't control their fan.

As for the GN switch, some places don't know what the hell a GN is, so you'll have to go the long way: tell em it's an "87 Buick Regal with a 4.6L turbo" and you need a "radiator fan switch" for it. Although when I asked for a Camaro fan switch at CarQuest, they gave me two choices, and the second choice was the same part number as the GN switch (TS-136).

In the picture you're talking about, the device to the left of the CTS is the Cold-Start Switch. It controls the 9th injector (aka Cold-Start Injector) on 85-88 TPI cars.

 

That makes a little more sence I thought I saw a wire going down that direction but never really followed it to see where it went, just assumed it was the fan switch every one talks about. But if I don't have this switch, then it seems to me that it's the ECM itself that is cause the fans not to come on, or am I overlooking something?

 

Pulled the wiring for 86 tpi. The fan relay is directly controlled by the ECM. There is no aux switch like the dual fan setups use. On carbed engines the ECM does NOT control fan relay. A simple switch is used similiar to the switch used for aux fan on 2 fan units. This switch controls the relay coil directly with no assistance from the ECM at all. If the fan is not coming on at all with stock wiring then either the CTS is not working(which will usually cause driveability problems and code)or there is a problem in the wiring from the ECM to the fan relay. A bad driver in the ECM could also be suspect. How did you hotwire the fan? Are you grounding the relay coil causing it to energize, or are you simply putting 12 volts to the feed wire for the fan? If you are actually energizing the relay and the fan works then the relay and connector are OK. At that point you will have to go to the ECM pin E8 with a voltmeter. With fan off it should be 12 volts, when engine comes to temp and fan action is called for it will go low. The ECM internal driver provides a ground for the one end of the relay coil, the other end goes directly to the vehicles 12 volt supply and will be hot in the run position. When you are sure you have the right pin on the ECM for fan control you can ground that pin and the fan should run. This will check everything from the ECM to the fans. If it does not run then check wiring and connectors. Make sure when working with the ECM that you know for sure what pins are what, or you may have a very expensive mistake.

 

Yup, I have my manual toggle switch spliced into the green/white wire about an inch and a half from the ECM so all the wiring is apparently up to snuff all the way down to the fan. Son of a *****, so I need a new ECM..

 

Ok, I just took the TA out for a drive and I don't think my ecm is as shot as I thought. My fan switch worked a few times but after about 3 times it wouldn't turn the fan anymore. I popped the hood and the fan was barely spinning at all. I'm going to check it out more when the thing cools down a little... but is this most likely a short or a heat soak issue?

 

Just what I surmised. Most likely the relay connector is bad. The fan relay can pass power to the fans but usually the coil part of the relay is at fault. BELIEVE ME, I have gone through this for the last 8 years. Toss me another thread, I will be glad to tell you how to fix it, and it AIN'T hardwiring the fans. When you do that, all you do is eventually FRY the ALT.

 

Actually it turns out the fan motor is bad. I jumped it to the positve battery terminal and nothing. Then my dad reached over and gave the fan blade a little nudge, and it started right up. Not sure why but it just doesn't have what it takes to get it started any more.

 

At what temp is the main fan supposed to turn on?
I was idling my car last night for around a half hour and the fans never kicked on. The car got to one notch above the 220 mark on the temp gauge before I shut it off.

I grounded the ALDL and the fan(s) kicked on. So obviously they themselves are working.
Ideas?

 

Let it crawl up to half way between 220 and 260, somewhere in there the fan should kick on.

 

I believe it is 222 deg. for stock setup. If it is a dual fan arrangement primary is 222, and secondary should come on around 238-240. Napa stocks 2 different secondary fan switches. The stock 238, and a lower one(not sure of temp). It is only $19 and is cheaper than the Jet switch if you want to kick the secondary on sooner. Remember the primary(2 fan models) is controlled by the ECM, the secondary is controlled by a temp switch on the passenger side of the block.

 

GM sure did put a high kick-on temp for these cars didn't they.

Thanks

 

Yeah, they sure did. Emissions, Emissions etc,etc. I changed my secondary switch 2 yrs ago to a Jet(on @205-off @185 with a 180 stat). After a couple of trips to the Jersey shore in traffic I put everything back to stock. The fans just cycled too much. Also the lower stat reduced fuel economy noticeably. You will hear a lot of differing opinions here about running cooler stats, but as I have found unless you get a custom Prom driveability always suffers. I equate fuel economy to efficiency, I got between 3-5MPG improvement by running stock stat. A lot of guys do put in a manual switch for fan control as an insurance policy, that's up to you.

 

I think I will put in a lower fan temp switch. I'm a bit uncomfortable with such high temps.
I have yet to actually see the fans run by themselves. My car never seems to get hot enough.
'course I just put in the stock stat, replaced the radiator, reverse flushed the system, and finished removing all AC components. All that makes for a cooler running car